In many types of confrontational situations, the use of lethal ammunition is not appropriate. More and more law enforcement and military authorities are seeking ways to reduce casualties in confrontation situations, particularly crowd control and in hostage situations, which are handled by special task forces, e.g. SWAT teams and air marshals. Different available less-lethal devices have been evaluated and categorized in terms of their effectiveness and potential in the context of law enforcement (“Less Lethal Technologies—Initial Prioritisation and Evaluation,” by T. Donnelley, Home Office, PSDB No. 12/01, Police Scientific Development Branch, Hertfordshire, United Kingdom (2002)”—with permission to quote). In this report, the impact type of less-lethal ammunition projectiles were placed in Category A, i.e. those devices meriting immediate further research. Examples of less-lethal ammunition projectiles given were bean bags, sock rounds, single and multiple ball rounds, fin stabilized rubber projectiles, single and multiple baton rounds and encapsulated rounds.
Fin stabilized rubber projectiles (referred to as the Rocket) are made of thermoset elastomers, for example EPDM (Ethylene-Propylene-Diene rubber). One specific sample analyzed was made of filled thermoset EPDM and was measured to have a density of 1.4 gcm−3, and Shore A Hardness (ASTM D2240) of 62. The fin stabilization improves the accuracy at long ranges. These projectiles are generally fired from a 12-gauge shotgun or compressed gas weapon and the typical range is up to 45 m. Drawbacks associated with these types of projectiles are their high fabrication cost and very small tolerances in the design dimensions. In addition, under cold climatic conditions (<0° C.) these projectiles “freeze’ i.e., become hard, and as a result can be lethal if for example they hit a person in the head or temple.
Another type of non-lethal ammunition, namely tail stabilized lead filled rubber projectiles (Tube) consist of a cylindrical envelope made of thermoset rubbers, for example EPDM or SBR (styrene-butadiene rubber). The core of the projectile is filled with lead pellets. The tail is attached to the projectile for stabilization, which improves its accuracy. One specific example analyzed was made of an SBR shell filled with lead pellets, and was measured to have a total density of about 4.1 gcm−3, with the density and Shore A hardness of the rubber shell being 1.2 gcm−3, and 62, respectively. These projectiles are generally fired from a 12-gauge weapon and the typical range is 5-30 m, depending on the model and type of weapon used. Drawbacks associated with these types of projectiles are their high fabrication cost, presence of lead and their ‘lethality’ under cold climatic conditions.
Another type of non-lethal ammunition, mono-ball rounds, consists of single rubber balls which are delivered over a short range. They are made of thermoset rubber, e.g., natural rubber, filled with mineral fillers, e.g., calcium carbonate. One specific example analyzed was made of filled thermoset polyisoprene (synthetic or natural) and was measured to have a density of 1.11 gcm−3 and Shore A Hardness of 46. Drawbacks associated with these projectiles include little or no accuracy. These projectiles are generally fired from a 37 mm weapon, which most police and military personnel find cumbersome to carry around.
Multi-ball rounds are another type of less-lethal impact projectiles which include multiple rubber balls delivered over a short range as these projectiles quickly loose their kinetic energy owing to their low mass. They are made of thermoset rubbers, e.g., natural rubber or SBR, filled with minerals, e.g., calcium carbonate or carbon black. One specific example analyzed was made of filled thermoset EPDM, and was measured to have a density of 1.1 gcm−3, and Shore A hardness of 62. These projectiles are generally fired from a 12-gauge weapon but other calibers may also be found. The range of these projectiles depends on the diameter and number of balls, the caliber of the projectiles and the amount of propellant. Drawbacks associated with these projectiles are that like single ball rounds, these projectiles are indiscriminate hence have little or no accuracy.
Beanbag rounds are another type of non-lethal ammunition which consists of a square or circular envelope of fabric containing lead shots. The beanbag is generally fired from a 12-gauge weapon and flattens on impact, thereby spreading the energy over a large area. The typical range is 5-30 m, depending on the model and type of weapon used. For example, a 12 gauge round contains two 2-inch beanbags, each filled with 20 grams of #9 Lead. A few shortcomings associated with beanbag projectiles include inaccuracy, failure to open up and hitting the target edge on (i.e., “Frisbee effect”). In addition, the fabric may tear, causing environmentally toxic lead pellets to spill over the target and causing serious injuries. These are the most widely used less-lethal impact projectiles in North America and are associated with a few fatal incidents.
Sock rounds, another type of less-lethal impact projectiles, were developed to overcome the shortcomings associated with bean bag rounds. The sock round consists of a “sock” filled with lead pellets. A long tail is attached to the sock to enhance the stability of the projectile during flight. The problems associated with sock rounds are inaccuracy, tear of fabric and presence of environmentally toxic lead.
Powder filled rounds are less-lethal impact projectiles made of very soft, highly pliant silicone rubbers filled with metal powder. These projectiles expand radially upon impact thereby spreading their kinetic energy over a large area. The problem associated with these rounds is high cost.
Another type of less lethal ammunition is baton rounds which where first used by the police in Northern Ireland in 1973 and have steadily evolved over the years. They are made of polyurethane-based thermoplastics and have oIRHD (ASTM D1415) hardness in the range of 85 to 95 and mass in the range of 90 to 100 g. The most common commercially available rounds are L5A7 and L21A1.
One of the major concerns for law-enforcement agencies in using these less-lethal ammunition projectiles is the delicate balance between their effectiveness and their lethality. For example, the sock rounds, (i.e., fabric filled with lead pellets) and rubber projectiles (i.e., solid or filled with lead pellets) which are presently being used for crowd control, have been found to be lethal within a short range or causing serious injuries to vital organs. The fabric or thermoset elastomers used for the manufacture of these less-lethal projectiles require intricate design and fabrication, which enhances their cost. In addition, the presence of environmentally toxic lead results in serious health safety concerns among law enforcement agencies. Literature survey revealed that less lethal ammunition presently being used are either made of thermoplastics or thermoset-based carbon black/calcium carbonate filled composites. They reportedly are capable of inflicting lethal injuries when shot from a short distance or when shot at a vital organ (R. I. H. Whitlock and J. M. Gorman, Int. J. Oral Surg. 7, 240-245 (1978).).
Recently, Cynthia A Bir of Wayne State University, Michigan (Evaluation of Blunt ballistic impacts: The establishment of human response corridors. Bir C A; Vino D C; King A I, Proceedings of the Non-lethal Conference IV, Tysons Corner, Va. (2000); Ph. D. Thesis, 2000), has analyzed the effect of blunt ballistic impact on the thoracic region using human cadavers. She determined the human response corridors and developed biomechanical surrogates, which can be used for testing different new projectiles for their blunt ballistic impact. In addition, a 3-Rib Ballistic Impact Device (3-RBID) was developed to simulate the human response to low mass, high velocity impacts to the chest region. The human response force corridor for blunt thoracic impact for a 30 g projectile traveling at 60 ms−1 (˜200 fts−1) was found to be in the range of 1800 N to 3800 N (400 lbf to 830 lbf). Based on this work, in the present invention, the optimum weight and impact energy requirements for the new less lethal projectiles were applied for designing the new less lethal projectile. In addition, this invention also presents a new method to measure the impact energy of new and existing less lethal projectiles. This new method uses a viscoelastic material, namely polystyrene foam (Styrofoam Impactor) to measure the impact energy of less-lethal projectiles. Traditionally, clay or gel are used to measure the impact energy of lethal projectiles. These are also viscoelastic materials, but are very sensitive to environmental conditions such as moisture level and temperature so need to be conditioned before use. The traditional method has been adopted to test less-lethal ammunition as well but due to the low impact force of less lethal projectiles it is not very satisfactory for this purpose.